The present invention relates to a motor vehicle and a method for operating a seat belt system in a motor vehicle.
A seat belt, also known as a safety belt, is a motor vehicle safety device designed to secure an occupant of the vehicle against harmful movement that may result during a collision or a sudden stop. A seat belt functions to reduce the likelihood of death or serious injury in a traffic collision by reducing the force of secondary impacts with interior strike hazards, by keeping occupants positioned correctly and by preventing ejection of the occupants from the vehicle in a crash or if the vehicle rolls over.
Safety belt systems typically include an insertable structure (or “tongue”) configured to mate with a buckle when inserted therein, so as to result in a fastened clasp. The buckle is firmly attached to a structural member of the vehicle seat or the vehicle itself. Conventional buckles are permanently fixed in position. Depending on the manufacturer's design, a conventional buckle is either constantly readily accessible, but always visible, or constantly hidden, but always in a difficult-to-reach position relative to the user.
In response to the afore-mentioned concerns, one proposal has been to use a safety belt buckle presenter to selectively cause the buckle to translate between deployed and stowed positions. Such a buckle presenter is operable to stow the buckle when it is not needed, and to automatically present the buckle when desired. As such, the buckle presenter is useful for aiding physically challenged users (e.g., the disabled, elderly, youth, etc.) to fasten their seat belts, and serves to remind and increase convenience for all users.
In order for the buckle presenter to operate effectively, the buckle must be presented at the proper time, when it is needed. One proposal is to detect when a vehicle occupant has sat in the corresponding vehicle seat. For example, buckle deployment may occur when a piezoelectric-based load sensor detects a force greater than a predetermined minimum, for example greater than 20 pounds. Based on the output of this sensor, it is concluded that the vehicle seat is occupied and the buckle is needed. However, the vehicle seat being occupied does not necessarily mean that the occupant is trying to fasten his/her seat belt.
Another way to control the buckle presenter is to use a sensor in a belt retractor. Modern seat belt systems commonly use a locking belt retractor to provide the seated occupant the convenience of some free movement of the upper torso, while limiting this movement in the event of a crash. The webbing of the seat belt is stowed on a spring-loaded reel within the retractor. This reel is equipped with an inertial locking mechanism that stops the belt from extending off the reel during severe deceleration.
A sensor can be provided on the spring-loaded reel to determine when the occupant is pulling the safety belt webbing toward the buckle. Thus, in addition to occupying the associative passenger seat, the triggering condition for the buckle presenter may be the act of pulling the safety belt webbing. Opening and closing a vehicle door are other possible triggering conditions. These triggering conditions may be more accurate than a seat sensor, but they require expensive sensors.
The buckle may be returned to a normal position either when the tongue is inserted into the clasp or, if the occupant has not fastened the seat belt, after a predetermined time has elapsed. However, these return triggering mechanisms do not fully consider the occupant's actions. Returning the buckle at the wrong time is inconvenient to the vehicle occupant and could even pinch the occupant's hands between the seat and the buckle.